- Before Mushashi's life went to hell, he was an extremely intelligent star student with the desire to become a doctor, and that intelligence hasn't gone away. Even though he's blind, he still can read brail in over a dozen languages, and is a major book nerd who's almost always reading in his free time. Thanks to his past, he also has no social skills or experience making friends, and often ends up sulking in a corner over his confusion about other humans.
- Nico is a cute and happy-go-lucky Otaku who loves playing games and often speaks in anime quotes.
- Awesome Music: Rin! Rin! Hi! Hi! is an unexpectedly catchy tune.
- Broken Base: The overall mood of the series is hard to read, and not everyone is pleased with the darker turn the series took after we're introduced to Musashi, and we learn about the human experiments performed on him and Jyugo. Some wanted a straight prison escape comedy, and others wish that they'd quit with the comedic bits since they're trying hard to present the serious moments as such.
- Ensemble Dark Horse: The inmates of Building 5 (Liang, Upa, and Qi) are quite popular amongst fans, particularly after Season 2 gave them some well-received backstories and Character Development. The same can be said for Building 3's inmates, Trois and Honey, whose personalities were fleshed out throughout the second season.
- Ho Yay: Jyugo and Uno are very close, and it was stated that the two have known each other for a long time. Uno is shown to be caring and protective towards Jyugo, such as when he tries to stop the latter's rampage at the New Years' Tournament, then practically explodes on Hajime for nearly beating him to death. On the other hand, Jyugo finds comfort in Uno's friendship, and even states that he found a reason to look forward to the next day due to a conversation the two had.
- Jerkass Woobie: Building 5's supervisor, Samon Gokuu. He's prone to angry outbursts, particularly at Hajime, but in the second season it's revealed that his brother, Enki Gokuu, had previously killed an inmate when he was still a guard, and Samon had to deal with the aftermath of his arrest, as well as the nasty rumors and taunting from other guards who believe him to be like his brother. Then Enki escapes, brutally beats Samon, and imprisons him in the underground cells for the rest of the season.
- Moe: Most fans of the series love Nico, as his optimistic personality and Otaku hobbies endear them to him.
- Likewise, Seitarou's shy and mellow nature are endearing to many fans.
- Spiritual Licensee: Can be viewed as the closest thing to an anime adaptation of Hogan's Heroes.
- Viewer Gender Confusion: Nico and Seitarou looked female to viewers at first glance. On the flip side, many mistook Momoko as male, probably due to her Spiky Hair and the series bursting with a Cast Full of Pretty Boys.
- The Woobie: As the series goes on, nearly every character falls into this at one point or another.
- Jyugo. As stated above, with the progression of the series, almost every character falls into this at one point or another. But Jyugo deserves a mention. Poor guy was born in prison and literally grew up in prisons, can't really function outside of it, and often gets teased for being incapable of anything except jailbreaking. It only gets worse during the New Years' Tournament, where his past of being cruelly treated as a test subject comes to light, and he's unwittingly sent on a vicious rampage, nearly killing his friends in the process. Afterwards, he's locked up in the underground cells for several days and then, when Hajime says that he is 'empty', he breaks down and admits that he has never wanted anything, and that he was jealous of his friends in Cell 13 because they had their own goals, hobbies and motivations for breaking out of the prison, while he has never had any of them. And who can blame him? The only things he has any knowledge about are prisons and jailbreaking, and he considers himself as an idiot for this, and not only an idiot, he also thinks he is a monster because of TMWTS's experiments on him. If this wasn't bad enough, he is now utterly terrified that his friends won't accept him as he unintentionally revealed that is a 'monster'. Things get better after he is released and accepted back into Cell 13 and Rock, Nico and Uno cheer him up. And after all this, when he finally feels that he can look forward to the next day and is really happy, Elf appears, brutally threatening him that the next person subjected to The Man with The Scar's experiments could very well be one of the only friends he absolutely treasures. Jyugo, convinced that he will doom them if he stays there any longer, goes up against Hajime, who has already beaten the shit out of him once, to escape alone. Said fight ends with with Rock, Nico and Uno blocking his escape and convincing him to stay with them. While it is a happy moment, he now has to live with the constant fear that Elf might one day come back and kill his friends if he keeps hanging around them. And then, it is later revealed that his past could possibly be even darker than initially shown because he eventually realizes that large parts of his memories are missing, and that they were likely wiped out by The Man with the Scar experimenting on him more intensely than he initially recalled. Phew.
YMMV / Nanbaka